It is common for molluscs such as oysters to be grown on a commercial scale in artificial environments in early stages of growth. Typically, the stock is then transferred to sea environments for what is known as “grow out”. Cultivation of oysters is accomplished by initially growing the lava in special tanks until they reach a juvenile size when they can be transferred to containers in intertidal or sub-tidal sites. Typically, the containers are in the form of baskets having perforated walls which enable water to flow through the baskets where the oysters use the water flow to obtain nutrients from the water as well as flushing impurities away.
In adjustable long line oyster cultivation, the baskets are typically suspended from lines that extend for hundreds of metres with multiple lines being attached in a parallel configuration according to an embodiment. These lines are typically made up of tensioned monofilament with a protective sheath or “drip tube” over the monofilament to reduce wear. Posts are used to support the tensioned line and are typically spaced at intervals along the line to allow for at least one basket to be suspended between adjacent posts. The drip tube typically extends the full length of the line. Special clips are used to attach the baskets to the drip tube, and can be attached both along the line (parallel arrangement) or across pairs of lines (perpendicular arrangement).
It has been recognised more recently that placing baskets in rougher waters can improve the growth of oysters. However, more aggressive water conditions have brought about problems not previously encountered in calmer water conditions. Most notably, it has been found that the clips used to rotatably attach the oyster baskets to the drip tubes are wearing, as are the drip tubes in areas where the clips attach. In rougher waters, it is not uncommon for clips and hence baskets to slide back and forth along the drip tube and collide with the support posts. Baskets have also been known to perform full 360 degree rotations about the line. This often results in winding of the drip tube and can also have adverse effects when, for example, winding occurs in opposite directions at opposite ends of the drip tube.
FIG. 1 illustrates an example of a known clip 2 including at one end a means of rotatable attachment 4 to an oyster basket and at the other end a means of rotatable attachment 5 to a drip tube 6 which acts as a protective sheath for the line 7. The rotatable attachment 5 is simply a hook means with an opening of sufficient size to receive the tube when the hook is forced down on the tube and to maintain the tube therein. The result is that the clip is slideable along the tube, but not easily removable unless the clip is forced in a direction away from the line. It is the areas indicated by reference numeral 8 on the clip and reference numeral 9 on the drip tube which would typically wear and render the clips and tubes unusable over time. The attachment portion 5 of the clip is such that the drip tube 6 needs to be secured therein, but when this part is sufficiently worn, the tube 6 can easily become detached from the clip.
The skilled addressee would understand the expense and labour that is required to replace these clips, and moreso to have to remove clips and baskets suspended on a line to enable a full replacement of the line.
It is therefore an object of the present invention to alleviate some of the aforementioned problems, or at least provide the public with a useful alternative.